Many pourable food products, such as beverages, fruit juice, pasteurized or UHT (ultra-high-temperature treated) milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material.
One example of this type of package is the gable-top package for liquid or pourable food products, as described in European Patent EP1440010 and in published Patent Application EP1584563, and known by the trade name Tetra Gemina™ Aseptic.
More specifically, the above package comprises a parallelepiped-shaped main portion; and a gable top portion defined by two sloping walls joined along a sealing strip.
More specifically, the walls of the gable portion are trapezoidal in shape, project from the main portion of the package at their respective major bases, and are joined by the sealing strip at their respective minor bases.
The gable portion comprises two lateral flaps folded outside the volume of the package available for the food product.
The flaps each project from a respective oblique side of a first wall, and are folded towards the second wall and superimposed, at the sealing strip, on respective oblique sides of the second wall.
The above package is produced by folding and sealing laminated strip packaging material.
The packaging material has a multilayer structure substantially comprising a base layer for stiffness and strength, which may comprise a layer of fibrous material, e.g. paper, or mineral-filled polypropylene material; and a number of layers of heat-seal plastic material, e.g. polyethylene film, covering both sides of the base layer.
In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material also comprises a layer of gas- and light-barrier material, e.g. aluminium foil or ethyl vinyl alcohol (EVOH) film, which is superimposed on a layer of heat-seal plastic material, and is in turn covered with another layer of heat-seal plastic material forming the inner face of the package eventually contacting the food product.
As is known, packages of this sort are produced on fully automatic packaging machines, on which a continuous tube is formed from the web-fed packaging material. More specifically, the web of packaging material is unwound off a reel and fed through an aseptic chamber on the packaging machine, where it is sterilized, e.g. by applying a sterilizing agent, such as hydrogen peroxide, which is subsequently evaporated by heating and/or by subjecting the packaging material to radiation of appropriate wavelength and intensity; and the web so sterilized is maintained in a closed, sterile environment, is folded into a cylinder, and is sealed longitudinally to form a continuous tube in known manner.
The tube of packaging material, actually forming an extension of the aseptic chamber, is fed continuously in a vertical direction, is filled with the sterilized or sterile-processed food product, and is fed through a forming unit for producing the individual packages. That is, inside the forming unit, the tube is sealed along a number of equally spaced cross sections to form a continuous strip of pillow packs connected to one another by respective transverse sealing strips, i.e. extending perpendicular to the travelling direction of the tube. And the pillow packs are separated by cutting the relative transverse sealing strips, and are then folded further to form respective finished gable-top packages.